United States
Environmental Protection
Agency
Hazardous Waste Engineering
Research Laboratory
Cincinnati OH 45268
^'f
Research and Development
EPA/600/S2-85/069 Jan. 1986
Project Summary
Evaluation of Emerging
Technologies for the
Destruction of Hazardous Wastes
Jan Radimsky and Arvind Shah
The objective of the full report is to
provide detailed information regarding
four innovative alternative technolo-
gies demonstration projects for treat-
ing and destroying hazardous wastes.
Under a cooperative agreement be-
tween the U.S. Environmental Protec-
tion Agency (EPA) and the State of Cal-
ifornia, the Department of Health
Services (DHS) carried out a pilot-scale
test program on the following promis-
ing technologies.
1. High Temperature Thagard
Fluid-Wall Research
2. Evaluation of Air Resources
Emission Tests Board State
from SunOhio of California
Mobile PCB
Treatment Pro-
cess
3. Wet Air Oxidation Zimpro
4. Evaluation of Air Resources
Emission Tests Board State
from Wet Air of California
Oxidation Zim-
pro Process
Discussions of the above processes
include project descriptions, results,
conclusions, and recommendations.
This Project Summary was devel-
oped by EPA's Hazardous Waste Engi-
neering Research Laboratory, Cincin-
nati, OH, to announce key findings of
the research project that is fully docu-
mented in a separate report of the same
title (see Project Report ordering infor-
mation at back).
Introduction
On January 20,1981, the State of Cal-
ifornia entered into a cooperative agree-
ment with the Office of Research and
Development, EPA, to evaluate selected
promising technologies for destroying
hazardous waste. The inclusion of a pro-
cess in the report should in no way be
considered an endorsement of the pro-
cess by either the State of California or
the EPA.
High Temperature Fluid-Wall,
Thagard Research Company
Summary
The High Temperature Fluid-Wall
(HTFW) Reactor was developed origi-
nally for the continuous dissociation of
methane into carbon fines and hydro-
gen. This particular process required
the generation of stable temperatures
above 1,700°C and the prevention of
precipitate formation on the reactor
walls. This fact has particular relevance
to the project herein.
Reactor consists of a tubular core of
porous refractory material capable of
emitting sufficient radiant energy to ac-
tivate the reactants fed into the tubular
space. The reactor has been built with
cylindrical core diameters of 3", 6", and
12" with heated core lengths of up to
'72". The core material is designed to be
of uniform porosity to aJlow the perme-
ating of a radiation-transparent gas
through the core wall into the interior.
The core is completely jacketed and in-
sulated in a fluid-tight pressure vessel.
Electrodes located in the annular space
between jacket and core provide the en-
ergy required to heat the core to radiant
temperatures.
To achieve both goals simultaneous-
ly, the reacting stream is kept out of
physical contact with the reactor wall by
means of a gaseous blanket formed by
flowing an inert gas radially inward
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through the porous reactor tube (or
core). Both high temperatures and high
rates of heat transfer are achieved by
heating the porous carbon core to in-
candescense so that the predominant
mode of heat transfer is by radioactive
coupling from the core to the stream.
Reactor is heated electrically with six
carbon resistance heaters. Because of
the extreme temperatures encountered
in operation of the device, the insulation
package consists not of refractory brick
but of a radiation shield made of multi-
ple layers of graphite paper backed up
with carbon felt. The short residence
time associated with the reactor which
demands the pulverization of solid
feeds also lends itself to a compact sys-
tem where a reasonably high through-
put is seen for a small installation, and
portability becomes an attainable de-
sign feature.
Four volatile chlorinated hydrocar-
bons [(dichloromethane; 1,1,1-
trichloroethane; carbon tetrachloride;
and Freon-12 (dichlorodifluorometh-
ane)] and one nonvolatile chlorinated
hydrocarbon (hexachlorobenzene) have
been decomposed in the HTFW Reactor
in bench-scale tests to assess the appli-
cability of the device for efficient de-
struction of these particular com-
pounds.
The hexachlorobenzene, loaded onto
a solid radiatiorvtarget, exhibited high
(O9.9999 percent) destruction effi-
ciency, while the vapors (which could
be heated only by secondary thermal
conduction from solid radiation target)
exhibited destruction efficiencies re-
lated inversely to the compound heats
of formation, indicating that vapor-
phase reaction temperatures were
lower than the solid reaction. Destruc-
tion efficiencies ranged from 99.999965
percent for dichioromethane to 84.99
percent for Freon-12. Heat transfer anal-
ysis indicated that vapor heating is de-
pendent on the solid particle density,
and that efficient heating (and destruc-
tion) of vapors can be achieved simply
by increasing the particle density.
Results and Conclusions
Chlorinated Hydrocarbon
Vapor Samples
The most important conclusion
drawn from the work completed is that
chlorinated hydrocarbons introduced
into the reactor in the vapor form are
much more difficult to destroy than sim-
ilar materials loaded onto solids, given
identical residence times and reactor
temperatures.
While the governing factor in the case
of the solids was the direct absorption
of radiation by the solid surfaces and
consequent extremely rapid heating,
the governing factor in the case of the
vapors was the conduction of the heat
from the particle surface into the
vapor—a much slower process limited
in rate by the thermal conductivity of
the vapor itself.
Thus, as might be anticipated, the
temperature levels achieved in the va-
pors for a given residence time will not,
in general, be as high as the tempera-
tures achieved on the solids. The exper-
imental result of this behavior will be
that minimum temperatures and mini-
mum residence times for complete de-
struction of the vapor-phase substances
will not be achieved, and that the ob-
served destruction levels will now be
critically dependent on the heat of for-
mation of the substance being investi-
gated.
Chlorinated Hydrocarbons
Solid Sample
The results for hexachlorobenzene
(HCB) in soil are in agreement with HCB
results on carbon, thus duplicating both
the destruction and analytical methods
and further substantiating the conclu-
sion that the solids are rapidly heated
and the toxic material effectively de-
composed.
Despite some data problems, the frac-
tion of HCB remaining on the solids and
in the effluent gases was approximately
10~6, corresponding to a destruction ef-
ficiency of approximately 99.9999 per-
cent.
The demonstration of gettering of
chlorine (from decomposition of HCB)
with calcined lime (CaO) mixed with the
soil produced no identifiable results.
Since gettering of halogens and sulfur
with lime and subsequent fixing into a
vitreous slag has been previously dem-
onstrated on numerous occasions with
other materials we must conclude that
some deficiency in the experimental
procedure was introduced (inadequate
mixing of the lime in the soil, too low a
CaO/CI ratio for this particular applica-
tion, etc.). Subsequent experimental
work will seek to quantify this parame-
ter which is an important system con-
sideration of on-site disposal.
Air Resources Board's (ARB)
Evaluation to Determine
Emissions from SUNOHIO's
Mobile PCB Treatment Process
Three evaluation tests were con-
ducted to allow determination of emis-
sions from SUNOHIO's mobile PCB
treatment process. The mobile unit was
tested while treating contaminated oils
at three locations: Chevron's USA refin-
ery at El Segundo, California; Pacific
Gas and Electric (PG&E) Company's fa-
cility at Union City, California; and
Maxwell Laboratory's facility in San
Diego, California.
PCBs were not detected in samples of
emissions taken at two of the tests.
However, relatively high benzene and
aliphatic hydrocarbon concentrations
were measured in the units' uncon-
trolled exhaust gases. Measured con-
centrations ranged from 18 to 7,000
ppm for benzene and 700 to 2,700 ppm
for aliphatic hydrocarbons. Low process
volumetric flow rates resulted in the
mass emission rates for benzene and
the aliphatic hydrocarbons to values of
approximately 0.1 Ib/hr. and below.
Data from samples taken by the South
Coast Air Quality Management District
(SCAQMD) staff during the El Segundo
test indicate that dioxins and furans are
not present above the limit of detect-
ability.
The efficiency of the carbon adsorp-
tion control system for preventing emis-
sions to the atmosphere of benzene and
aliphatic hydrocarbons was found to
have varied from approximately 99 to
30 percent, indicative that carbon ad-
sorption breakthrough occurred. The 30
percent efficiency calculation was
based upon concentration measure-
ments from the evaluation test con-
ducted at the PG&E facility.
An alternative control system was
tested that utilized an oil fired furnace, a
component of the PCBX process, to in-
cinerate the emissions. Furnace exhaust
gas samples indicate a general reduc-
tion in concentration of compounds
measured across the furnace. Benzene
and toluene were not detected in the
furnace exhaust gas.
Introduction
On December 2 and 10, 1982 and No-
vember 30,1983, the ARB's Engineering
Evaluation Branch conducted evalua-
tion tests on chemical processing
equipment designed to reclaim trans-
former oils contaminated with PCBs.
The process tested is known as the
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"PCBX" process and was developed by
SUNOHIO, a partnership between the
Sun Company of Radnor, Pennsylvania
and the Ohio Transformer Corporation
of Louisville, Ohio. The equipment is in-
stalled on two mobile trailers and can
be driven to different geographical lo-
calities to treat contaminated oils on
site. The first test was conducted on De-
cember 2,1982 at Chevron's USA El Se-
gundo refinery. This was a joint venture
between SCAQMD and the ARB. The
second test was conducted on Decem-
ber 10, 1982 at a PG&E facility in Union
City. The third test was conducted on
November 30,1983 at the San Diego fa-
cility of Maxwell Laboratory.
The objectives of the evaluation tests
were to allow determination of emis-
sions from the unit's vacuum degasser
and determination of the efficiency of
two prototype emission control sys-
tems. One control system consists of an
oil mist eliminator, in combination with
an activated charcoal filter to control
emissions from the vacuum degasser's
vent pipe. The other control system uti-
lizes an oil fired furnace that is a compo-
nent of the PCBX process to incinerate
the emissions.
Conclusions and
Recommendations
Based on the analytical results and
staff experience obtained from the
ARB's evaluation test conducted on the
SUNOHIO PCBX process, the following
observations are made:
1. The activated carbon adsorption
canister used during testing is not
big enough to provide effective
emissions control for an extended
period of time, the control system
should be (1) redesigned to have a
larger activated carbon adsorption
unit, or (2) revise the maintenance
schedule for the present carbon
canister to require canister re-
placement with a frequency com-
mensurate with a demonstrated
breakthrough* time.
2. If emissions are to be prevented
from the carbon canister, the car-
bon canister breakthrough should
be monitored with a continuous
analyzer.
3. Based upon the results of this test,
the oil fired furnace as a control
device appears to,be effective.
Results and Discussion
1. Results From the Test Conducted
at Chevron's USA El Segundo Re-
finery
Results of analyses performed on
samples taken from the PCBX pro-
cess during the ARB evaluation
test conducted at Chevron's USA
El Segundo refinery indicate that
Benzene and Ca-C^ hydrocarbons
were the predominant compo-
nents measured in the gases
vented directly out of the vacuum
degasser during the treatment of
transformer oil. Benzene concen-
trations ranged from 400 ppm to
7,000 ppm and hydrocarbon con-
centrations from 7 ppm to 1,600
ppm. TRW's analytical results for
samples taken at the same location
as the ARB, show benzene concen-
trations exceeding 5,000 ppm and
C5 hydrocarbon concentrations as
being 1,400 ppm. TRW results for
benzene are in the range of con-
centrations determined by the ARB
and the hydrocarbon concentra-
tions, while not directly compara-
ble to the ARB results, are proba-
bly not inconsistent. SCAQMD did
not take samples from the vacuum
degasser outlet.
PCBs were not detected above the
detection limit of the analytical
method for any of the ARB sam-
ples taken. TRW also sampled for
and could not detect PCBs above
the limit of detection for their ana-
lytical method (1 ppm).
As discussed previously, SCAQMD
took samples before and after the
activated carbon adsorber and an-
alyzed those samples for PCBs,
furans, and dioxins. Because they
sampled at a different location and
the emphasis of their analytical
work was different, no direct com-
parison can be made between the
SCAQMD and ARB test results.
Test results indicate that furans
and dioxins are not present above
the detectable limits, less than 4-30
parts per trillion. However, in two
samples taken from the centrifuge
vent at the inlet and outlet of the
carbon cannister, detectable
amounts of PCBs were measured;
1..7 (10~3) ppm at the inlet and 8.7
(10~6) ppm at the outlet.
2. Results From the Test Conducted
at PG&E's Union City Facility
Benzene and aliphatic hydrocar-
bons were the major components
measured in the ARB samples
taken from the degasser vent dur-
ing the treatment of PCB-
contaminated oils stored in a tank
at a PG&E facility located in Union
City. The range of concentrations
determined for benzene and Ce-C^
hydrocarbons was 50 to 950 ppm
and 1,900 to 2,700 ppm, respec-
tively.
Benzene and aliphatic hydrocar-
bons were also the significant
components in the treated vacuum
degasser vent gas as sampled at
the outlet from the control sys-
tem's activated charcoal adsorber.
The range of benzene concentra-
tions was 600-700 ppm and the
range of Ce-C^ hydrocarbons was
1,400 to 1,800 ppm. BAAQMD also
took samples at the charcoal ad-
sorber outlet and test results
showed: a comparable benzene
concentration of 840 ppm (aver-
age); a comparable C6-Ci2 hydro-
carbon concentration of 1,500
ppm; and total organic and non-
methane organic compound con-
centrations of 2,600 ppm (average)
and 2,400 ppm (average), respec-
tively.
The control system's charcoal can-
ister was the same one used at the
El Segundo test. Results of a com-
parison between the concentra-
tions determined for the inlet and
outlet of the control system are in-
dicative of carbon adsorption
breakthrough. The reduction of
both benzene and aliphatic hydro-
carbons was approximately 30
percent across the control system.
PCBs were not detected above the
detection limit of the analytical
method for any of the ARB sam-
ples taken.
3. Results From the Test Conducted
at the Maxwell Laboratory in San
Diego
Concentration values for emis-
sions were measured during two
distinct phases of the PCBX pro-
cess: (i) degassing and (ii) dechlo-
rination. Benzene concentrations
in the uncontrolled vacuum de-
gasser emissions, measured at the
common inlet to both control sys-
tems, ranged from 18 ppm to 220
ppm. Toluene was also measured
at concentrations ranging from 0.1
ppm to 290 ppm.
At the outlet from the condenser/
carbon control systems, measured
benzene concentrations ranged
from 10 ppm to 23 ppm and
toluene from 0.1 ppm to 26 ppm.
Benzene and toluene were not
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measured above the 0.1 ppm limit
of detection in the exhaust gases
from the combustion control de-
vice.
Products of combustion in the fur-
nace exhaust gas were monitored
when the furnace was fired on fuel
oil only and when it was fired with
a mixture of fuel oil and vacuum
degasser vapors. When combust-
ing fuel oil only, the following
compounds were measured: 75
ppm S02, 72 ppm NOx, 9.3 ppm
THC, 133 ppm CO, 10.2 percent
C02 and 9.7 percent 02. When vac-
uum degasser vapors were added
for combustion in the furnace,
measured concentrations were: 78
ppm S02, 92 ppm NOx, 24 ppm
THC, 200 ppm CO, 10.2 percent
C02, 9.1 percent 02, 0.1 ppm ben-
zene and 0.1 ppm, toluene.
Samples taken before and after the
control devices were speciated to
determine the types of compounds
present in the emissions. For com-
parison purposes, a sample of am-
bient air was taken. The com-
pounds detected in the ambient
sample were all at the part per bil-
lion (ppb) level. The magnitude of
the other concentration values
measured in the uncontrolled and
controlled emissions were at the
part per million level.
Commercial Demonstration of
Wet Air Oxidation of Hazardous
Wastes
Summary
Wet Air Oxidation by Zimpro, Inc., is a
process which has been used to oxidize
dissolved or suspended organic sub-
stances at elevated temperature and
pressures. The process is thermally
self-sustaining with relatively low or-
ganic feed concentrations and is, there-
fore, most useful for wastes which are
too dilute to incinerate economically yet
too toxic to treat biologically.
The purpose of this project was to
demonstrate wet air oxidation of toxic
and hazardous wastes at a full-size in-
stallation which was located at Cas-
malia Resources, a commercial waste
treater in California. In the operation of
the full-scale Zimpro Wet Air Oxidation
unit, wastes selected from classified
groups of organic wastes were detoxi-
fied. These classified groups were: phe-
nolic wastes, organic sulfur wastes,
general organic wastes, cyanide
wastes, pesticide wastes, and solvent
still bottoms wastes. This section con-
tains detail evaluation of these six clas-
sified wastes' treatment, the effective-
ness of the wet air oxidation unit, and
sample analysis of feed and effluent.
Description of Wet Air
Oxidation Process
The Zimpro Wet Air Oxidation unit for
this demonstration processed aqueous
wastes at a designed reactor tempera-
ture of 550°F, a designed reactor pres-
sure of 2,000 PSIG, a liquid waste flow
rate of 10 GPM, and a compressed air
rate of approximately 190 SCFM. In the
wet oxidation process, liquid waste, ex-
iting from a high pressure pump, is
combined with compressed air and di-
rected through the cold, heat-up side of
the heat exchanger. The incoming
waste-air mixture exits from the heat-up
side of the heat exchanger and enters
the reactor where exothermic reactions
increase the temperature of the mixture
to a desired value. The waste-air mix-
ture exits the reactor and enters the hot,
cool-down side of the heat exchanger
and, after passage through the system
pressure control valves, is directed to
the separator. In the separator, the
spent process vapors (noncondensible
gases) are separated from the oxidized
liquid phase and are directed into a
two-stage water scrubber-carbon bed
adsorber, vapor treatment system.
In the wet air oxidation process, or-
ganic substances can be completely ox-
idized to yield highly oxygenated prod-
ucts and water. For example, organic
carbon-hydrogen compounds can be
oxidized to carbon dioxide and water,
while reduced organic sulfur com-
pounds (sulfides, mercaptans, etc.) and
inorganic sulfides are easily oxidized to
inorganic sulfate, usually present in the
oxidized liquor as sulfuric acid. Inor-
ganic cyanides and organic cyanides
(nitriles) are easily oxidized to carbon
dioxide, ammonia, or molecular nitro-
gen. It should be noted that oxides of
nitrogen such as NO or N02 are not
formed in wet air oxidation.
When incomplete oxidation of or-
ganic substances occurs, the easily oxi-
dized reduced sulfur and cyanides are
usually still oxidized to sulfate and car-
bon dioxide-ammonia provided a suffi-
cient degree of oxidation is accom-
plished. However, incomplete oxidation
of other organic compounds results in
the formation of low molecular weight
compounds such as acetaldehyde, ace-
tone, and acetic acid. These low molec-
ular weight compounds are volatile and
are distributed between the process
off-gas phase and the oxidized liquid
phase. The concentration of these low
molecular weight compounds (mea-
sured as total hydrocarbons (THC) ex-
pressed as methane) in the process of
off-gas is dependent on their concentra-
tion in the oxidized liquid phase, which
is determined by the degree of oxida-
tion accomplished, the waste being oxi-
dized, and the influent organic concen-
tration of the waste.
Results and Conclusion
Wet air oxidation of phenolic and or-
ganic sulfur classes of waste has been
demonstrated at the Casmalia Re-
sources, Inc., full-scale wet air oxidation
installation. Oxidation of a petroleum
refining spent caustic waste at a process
temperature of 515°F (268°C) and a
nominal residence time of 113 minutes
resulted in 99.77 percent total phenols
reduction, 94.0 percent organic sulfur
reduction, and 89.3 percent chemical
oxygen demand (COD) reduction. Gas
chromatographic/mass spectroscopic
(GS-MS) analysis identified acetic acid,
benzoic acid, and several sulfide deriva-
tives as the major components present
in the effluent oxidized waste. Analysis
of treated process off-gases indicated a
total hydrocarbon (THC) concentration
of only 84.5 ppm (expressed as
methane).
Oxidation resulted in >99.7 percent
sulfide sulfur reduction, 98.8 percent
total phenols reduction, and 81.3 per-
cent COD reduction. Sulfide sulfur and
total phenols concentrations were re-
duced to > 1.0 mg/l and 66 mg/l, respec-
tively, upon oxidation. Further reduc-
tion in residual total phenols
concentration would likely be achieved
by postoxidation treatment with ozone
or hydrogen peroxide.
The raw spent caustic wastewater
had a BODs/COD ratio of 0.49 compared
to 0.64 for the oxidized product indicat-
ing a slight increase in biodegradability
following oxidation. The oxidized prod-
uct would likely be easily biodegradable
since highly biodegradable materials
generally have BODs/COD ratios in the
range of 0.5 to 0.6. The wastewater pH
decreased from 12.6 in the raw waste to
8.7 upon oxidation, likely due to the
conversion of reduced sulfur com-
pounds to sulfuric acid.
An eight-hour wet air oxidation dem-
onstration of a general organic waste-
water was performed at the Casmalia
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Resources, Inc., full-scale wet oxidation
installation on July 28, 1983.
The general organic wastewater was
processed continually during the eight-
hour wet air oxidation demonstration.
During the demonstration period, the
wet air oxidation unit was operated at
an average reactor temperature of 531°F
(277°C), a compressed air flow rate of
190 SCFM and a reactor pressure of
1,515 PSIG. Waste was processed at an
average liquid flow rate of 5.0 GPM re-
sulting in a nominal residence time of
120 minutes. Residual oxygen concen-
trations in the process off-gas averaged
4.1 percent during the demonstration
period.
The data indicates the waste to be rel-
atively high strength with a chemical
oxygen demand (COD) of 76.0 g/l and a
dissolved organic carbon (DOC) con-
centration of 20,830 mg/l. The raw
waste had a pH of 1.9. Very effective
treatment of the general organic waste
was obtained by wet air oxidation. Oxi-
dation resulted in 96.7 percent COD re-
duction with the waste COD reduced to
2.5 g/l. A DOC reduction of 96.7 percent
was obtained with the oxidized waste
having a DOC concentration of 685 mg/l.
Analysis of the off-gas sample indi-
cated carbon dioxide, oxygen, nitrogen,
and carbon monoxide concentrations of
12.9, 5.9, 81.2, and 0.3 percent, respec-
tively. Total hydrocarbon (THC) and
methane concentrations of 29.1 ppm
(expressed as methane)'and 10.0 ppm,
respectively, were determined for the
process off-gas sample.
Treatment of cyanide wastewafers by
wet air oxidation has been demon-
strated at the Casmalia Resources, Inc.,
full-scale wet air oxidation installation.
The wet air oxidation demonstration
was performed on July 29 and August
18,1983 during a combined six-hour pe-
riod of steady state operation.
The wastewater processed during the
wet air oxidation demonstration was a
mixture of cyanide wastes generated by
various metal plating processes. Labo-
ratory screening tests performed by
Zimpro, Inc., indicated the individual
wastes contained in the wastewater
mixture to be treatable by wet air oxida-
tion and compatible with respect to ma-
terials of construction.
During the combined demonstration
period, the wet air oxidation unit was
operated at an average reactor temper-
ature of 495°F (257°C), a compressed air
flow rate of 190 SCFM, and a reactor
pressure of 1,220 PSIG. Waste was pro-
cessed at an average liquid flow rate of
7.5 GPM, resulting in a nominal resi-
dence time of 80 minutes. Residual oxy-
gen concentrations in the process off-
gas averaged 7.1 percent during the
demonstration period. The analyses in-
dicate the composite raw waste to be a
typical high strength cyanide waste
with a cyanide concentration of 25,390
mg/l, chemical oxygen demand (COD)
of 37.4, g/l and pH of 12.6.
Wet air oxidation resulted in very ef-
fective treatment of the cyanide waste.
The cyanide concentration of the raw
waste was reduced to 82 mg/l, repre-
senting a cyanide reduction of 99.7 per-
cent. A COD reduction of 88.8 percent
and a dissolved organic carbon (DOC)
reduction of 88.4 percent were obtained
by wet air oxidation. COD and DOC con-
centrations in the composite oxidized
waste were 4.2 g/l and 1,710 mg/l, re-
spectively.
The scale formation which occurred
in the oxidation unit during the cyanide
demonstration period is reflected by the
total ash data. The composite raw waste
had a total ash concentration of 112.9 g/l
compared to only 77.4 g/l for the com-
posite oxidized waste. Since the ash is
expected to pass through the oxidation
unit as inert material, the data indicates
as much as 35 g/l of inert solids were
deposited in the oxidation system dur-
ing treatment of the cyanide waste.
Analysis of the off-gas sample indi-
cated 1.5 percent carbon dioxide, 8.5
percent oxygen, and 82.8 percent nitro-
gen. Carbon monoxide was not de-
tected in the off-gas sample. A total hy-
drocarbon (THC) concentration of 61.1
ppm (expressed as methane) and a
methane concentration of 9.0 ppm was
determined for the process off-gas sam-
ple.
Wet air oxidation of four pesticides—
dinoseb, methoxychlor, carbaryl, and
malathion—was evaluated in a full-
scale demonstration at Casmalia Re-
sources, Casmalia, California, on March
28, 1984. Since wastewaters containing
relatively high concentrations of a vari-
ety of pesticides were not easily avail-
able, the above compounds were
spiked into an acidic distillate waste-
water which had previously been pro-
cessed in the Casmalia wet air oxidation
unit.
Prior to the full-scale pesticides wet
air oxidation demonstration, bench
scale autoclave oxidations of a variety
of pesticides had been evaluated.
Greater than 99 percent destruction was
observed for seven pesticides, includ-
ing the four subsequently demon-
strated in the Casmalia full-scale unit.
Removals of the four pesticides
ranged from 98.0 to greater than 99.8
percent. Analyses of pesticides in the
feed and effluent composites were by
gas and liquid chromatography.
COD, BOD5, and DOC removals were
quite similar to results obtained during
oxidation of the acidic distillate waste
alone. COD, BOD5, and DOC removals
of 95.3, 93.8, and 96.1 percent were ob-
served. Carbon dioxide, oxygen, nitro-
gen, and carbon monoxide concentra-
tions of 14.2, 3.5, 79.0, and 0.7 percent,
respectively, were observed. Total hy-
drocarbon (THC) and methane concen-
trations of 153 ppm (expressed as
methane) and 61.9 ppm, respectively,
were determined for the process off-gas
sample.
Wet air oxidation of a solvent still bot-
toms type waste was evaluated in a full-
scale demonstration at Casmalia Re-
sources, Casmalia, California, on March
29, 1984. The wastewater was pro-
cessed continuously during the eight-
hour wet air oxidation demonstration.
Soluble chloride analyses for feed
and effluent indicated 7,860 and 505
mg/l, respectively. These data indicate
material in the feed causing a positive
interference 'in the chloride analysis.
Oxidation of this material resulted in an
apparent decrease in -soluble chloride.
This behavior is frequently seen in the
wet air oxidation of industrial wastes.
Soluble fluoride increased from 7.5 to
42.7 mg/l upon oxidation, likely due to
the destruction of fluorinated organic
compounds. This fluoride content was
not observed in previous bench scale
screening of this wastewater. Fluoride
levels much higher than this may not be
acceptable in the Casmalia wet air oxi-
dation unit because of corrosive effects
on titanium system components.
Carbon dioxide, oxygen, nitrogen,
and carbon monoxide concentrations of
11.8, 3.8, 81.2, and nil percent, respec-
tively, were observed. THC and
methane concentrations of 217 ppm
(expressed as methane) and 80 ppm, re-
spectively, were determined for the pro-
cess off-gas sample. However, on-line
off-gas THC measurements indicated
increasing THC concentrations through-
out the demonstration run as the vapor
phase activated carbon adsorption bed
became exhausted.
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Air Resources Board's
Evaluation Test Conducted on a
Wet Air Oxidation Process to
Treat Hazardous Wastes
Summary
The California Air Resources Board
(ARB) conducted six evaluation tests on
a wet air oxidation unit manufactured
by Zimpro, Inc. The unit designed to
treat toxic wastes is installed and oper-
ated at a Class I waste disposal facility
managed by Casmalia Resources and
located in Casmalia, California. The test
results of the four category wastes,
namely—phenols, sulfides, acid organ-
ics, and cyanides—are discussed in the
full report.
The ARB evaluation tests were initi-
ated in response to a request by Santa
Barbara County Air Pollution Control
District for emission data with which to
properly establish and assess the wet
air oxidation unit's waste processing ca-
pabilities and the effectiveness of the air
pollution control devices.
Results and Discussion
1. Wet Air Oxidation Process
Wet air oxidation appears to be an
effective method for reducing the
concentration of liquid phase
cyanide and phenol compounds.
Cyanide concentrations measured
at the inlet and outlet of the wet air
oxidation process were 46,300
parts per million by weight (ppm
W) and 6.94 ppm W, respectively.
Inlet and outlet phenol concentra-
tions were 18,700 micrograms per
milliliter (jjig/ml) and 2.35 (jig/ml.
The reduction in concentration for
both compounds treated by the
wet air oxidation process was over
99 percent.
However, wet air oxidation of acid-
organics was somewhat less con-
sistent. Two sets of inlet-outlet
samples were taken across the
process with one indicating a 64
percent reduction of the initial con-
centration and the other, a 97 per-
cent reduction. Each value was ob-
tained by ratioing the GC/FID
generated total peak areas for an
inlet-outlet sample pair taken
across the wet air oxidation pro-
cess. When the output sample's
GC/FID trace was compared to that
for the inlet sample, some peaks
had disappeared, some were no-
ticeably reduced, and in some in-
stances, new peaks appeared. Be-
6
cause the availability of standards
to identify each peak was limited,
the ratio of total peak areas was
used to give a relative indication of
the wet air oxidation process.
2. Condensible, Noncondensible
Separator
With the exception of acid-
organics, the amount of noncon-
densible cyanide, phenols, and
sulfide measured at the separator
was at the microgram level. The
quantity of CN, phenol, and sulfide
captured was 3.23 |xg, and 713 jxg,
respectively. These values also
represent the prescrubbed gas
concentrations at the inlet to the
scrubber. The total volume drawn
for each sample was 45 cubic feet.
A "less than" symbol (<) preced-
ing a value implies that it is below
the detection limit of the analytical
method with respect to the total
volume sampled.
Noncondensible acid-organic
samples taken at the separator
were used to identify and semi-
quantitate the major organic com-
ponents present in the gas stream
prior to entering the control equip-
ment. The results show that for the
treatment of this particular waste,
halogenated (bromo-, chloro-)
alkenes and benzene appear to be
the major compounds in the gase-
ous effluents from the separator.
3. Scrubber
The scrubber was effective in re-
moving sulfide from the gas
stream but did not afford any
greater control advantage for
cyanide and phenols than was
achieved by the wet air oxidation
process.
The calculated cyanide concentra-
tion at the inlet was very low,
0.0025 jxg/l or 0.0034 ppm.
The measured scrubber efficiency
for controlling noncondensible
sulfide was 93.4 percent. The
scrubber reduced the inlet concen-
tration of 0.555 |jig/l, or ppm, to
0.037 (i.g/1, or ppm.
The outlet cyanide concentration
of 0.0026 jig/l, <0.0025 ppm is
comparable to the inlet concentra-
tion and indicates that the scrub-
ber has no apparent effect on
cyanide when this compound is in-
troduced into the scrubber at such
low levels.
It appears that a major portion of
the residual phenols and cyanides
remaining after the wet air oxida-
tion process is retained in the sep-
arator's liquid phase and pumped
to the facility's water discharge
pond. Any liquid phase reactions
that may be occurring are un-
known. There is a minimal contri-
bution of cyanide and phenols to
the gas phase for control by the
scrubber. However, whether the
scrubber would be an effective
control device at higher inlet con-
centrations of cyanide and phe-
nols, as might occur during an
upset condition, is yet to be deter-
mined.
4. Carbon Bed
The carbon bed was most effective
in controlling the discharge to at-
mosphere of gas phase bromi-
nated compounds. The inlet con-
centration of 450 ppm was
reduced to 0.18 ppm at the outlet
of the carbon bed, representing a
removal efficiency of over 99 per-
cent. Note that these concentration
values are order of magnitude esti-
mates based on (a) the qualitative
speciatipn data that identified
brominated hydrocarbons as the
major noncondensible hydrocar-
bons present and (b) quantitative
analysis that normalized all
significant GC peaks to 1,2-
dibromomethane, which was the
major identifiable compound for
which a standard was available.
The normalization technique was
performed because standards
were not available for the other
major peaks. A comparison of
these values will give a relative ef-
ficiency performance of the carbon
adsorber.
The percentage control for cyanide
and sulfide was minimal: 17.8 per-
cent and 26.8 percent, respec-
tively.
The full report was submitted in par-
tial fulfillment of Cooperative Agree-
ment No. R-808908 under sponsorship
of the EPA and the State of California,
DHS.
U. S. GOVERNMENT PRINTING OFFICE:1986/646-l 16/20750
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Jan Radimsky and Arvind Shah are with Department of Health Services,
Sacramento. CA 95814.
Harry M. Freeman is the EPA Project Officer (see below).
The complete report, entitled "Evaluation of Emerging Technologies for the
Destruction of Hazardous Wastes," fOrder No. PB 86-128 717/AS; Cost:
$16.95, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield. VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Hazardous Waste Engineering Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
Official Business
Penalty for Private Use $300
EPA/600/S2-85/069
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